Self-leveling instrument mounting



April 13, 1954 J. F. EVANS sELF-LEvELTNG INSTRUMENT MOUNTING Filed Aug.i?, 1949 8 w 2 2 O 3 6 3 P N 2 O ww 2 2 M 3 5 6 4 ...2. l .y -HHH l--.1\ ||l| lllllu A l .l lll 3 MN HU n...,.. 8 5 Il M 5 -2 -l 5 7 5g 3 9.-O 4 L 4 4 u 2 6 INVENTOR. Julian F. Evans BY W @fm Afforne Patented Apr.13, 1954 f.. l 2,674,886

UNITED STATES PATENT OFFICE 2,674,886 SELF-LEVELING INSTRUMENT MOUNTINGJulian F. Evans, Tulsa, Okla., assignor to Stanolind Oil and GasCompany, Tulsa, Okla., a corporation of Delaware Application August 17,1949, Serial No. 110,855 4 Claims. (Cl. I3-382) This invention relatesto instrument mountings invention is a gravity meter suspension of theof the self-leveling type, and is directed particutype described,including means for establishing larly to a self-leveling mountingsuitable for a electrical circuits to the suspended gravity metervgravity meter such as is used in marine geo- Without introducingfrctional eects or torques physical surveying, 5 which interfere withits accurate leveling. Other In the application of the gravity meter togeoobjects, fuses, and advantages of the invention will lphysicalsurveying for petroleum in marine areas, become apparent as thedescription proceeds. it has so far been necessary to place the instru-The foregoing and other objects of my invenment on the floor of the bodyof water for the tion are attained in a suspension System Which reasonthat suiiicient sensitivity cannot ordinarily may be generally describedas a pair of members, be obtained with meters capable of being readpreferably in the form of concentric spherical on a moving platform,such as is provided by a bowls, with the gravity meter located inside ofvessel. These submersible 'gravity meters are, the inner bowl and a bodyof liquid, more or less in general, of two types: either a conventionalbuoyantly supporting the inner bowl and its load land gravity metermounted inside a diving bell l5 located between it and the outer bowl.The pivotwhich also allows space for an observer to be ing of the innerSpherical bowl iS as nearly aS lowered along with the meter to thebottom of the possible at the geometrical center of the two conwater; ora remote-control type of meter in which Centric Spherical SurfaoeS- Bymaking the buoythe instrument is placed in a water-tight conancy of theiuid as nearly as possible equal to tainer and lowered to the marinebottom, with the weight of the suspended system, and by prothe variouscontrols being provided by suitable viding a fluid of chosen relativelyconstant viselectrical or other connections extending from the cosity,both buoyancy and damping of the inner transporting vessel at the waterssurface. It is spherical bowl containing the gravity meter are to thelatter type that the present invention is accomplished, and the pivotingcan be provided especially applicable. by very delicate bearings.Further, if these bear- It is in connection with such remotely coningsare defective in any manner, so that normal trolled gravity meters thatproblems of accurately leveling would be interfered with, the buoyancyand quickly leveling the instrument after it has of the fluid acts onthe system in the proper come to rest on the marine floor have arisen.direction to restore the level to the proper value. Remotely controlledleveling devices, operated by This Will be better understood byreference to electric motors and indicating at the surface, have theaccompanying drawings Showing an illusbeen used; but these addconsiderably to the buik trative embodiment of the invention, in whichthe and complexity of the surface and subsurface Same numerals in thedifferent iigures refer to the equipment. A further difficulty withmotor-opsaine or Corresponding Darts- In the draWingSl erated levelingdevices, either manually or auto- Figure 1 shows a gravity meter mountedin acmatically controlled, is that a combination of ne oordanoe with theinvention as it is used in a adjustment and fast operation is difcult tobody of Water, Shown in cross-section, and achieve. Gimbal mounting ofthe gravity meter Figure 2 shows in detail a cross-section of theinstrument has been tried, but because of the acspherical mounting ofthe gravity meter. 1 curacy necessary to be obtained in the levelmgReferring now to these drawings, and to Figure process, very smallfrictional effects in the gimbal l in particular, the gravity meter iscarried with- -bearings and similar defects of pivoting of the in aspherical container in, mounted on a horisuspended system haveintroduced errors. Zontal framework H which rests upon and dies It isaccordingly a primary object of my inveninto the soft mud of the marinefloor i2, providing tion to provide an improved and simple suspenastable support for the gravity meter. In use, sion system for veryaccurately and rapidly selfthis assembly is manipulated from atransporting leveling an instrument such as a gravity meter vessel I3 bymeans of a lifting cable I, the vessel lused in marine work. Anotherobject lis to probeing held at a reading location by an anchor and vide,for a marine gravity meter, a particular chain l5. The gravity meterwithin container or type of suspension which provides simultaneouslyhousing is remote-controlled from the vessel I3 both support anddamping, permitting the use of by a multiple-conductor, insulatedelectric cable very delicate pivots without danger of damage :i 6, payedout from a reel il on the vessel when the thereto together with viscousdamping which very assembly is lowered to the marine ioor l,2 vvquiclttly brings the gravity-meter container to rest Referring now toFigure 2, the submersible ,in a'truly level position. A further objectoi the 55 spherical unit l0 comprises the Vtwo hemispnericai shells 2land 22 sealed and held together by a flange 23. The electricalmultiple-conductor cable Iii passes through an opening in the shell 22sealed by a waterproof lpacking `gland 2li. Although this sphericalhousing iii is probably the most desirable shape to withstand highhydrostatic pressures, and nts the equipment inside it most compactly,it could be of any other shape, if desired for speciiic reasons.

Within the watertight spherical shell thus provided is the gravity meterself-leveling mounting comprising an outer spherical bowl 25, and aninner spherical bowl 21 separated therefrom by a narrow space 2? partlyiilled` by a viscous fluid 25. Fixed to the inside of inner bowl 21 is awhich may be a conventional type of meter used for surveying on land,with Selsyn motor remote controls substituted for the various manualcontrols. As the particular form of this Vmeter is unimportant in thepresent invention, no urther description oi it is considered necessaryor will be given. Also, it will be observed that only the bowl surfacescontacted by the liquid 2S need be truly spherical. The other surfacesmay be o any form only roughly spherical, as ing.

The mounting oi gravity meter container 39 fixed to the inner bowl 21comprises the gimbal ring inner bearing 3 i, the gimbal ring 32, and thegimbal ring outer bearings 33 and 34, respectively carried by downwardlyprojecting arms 35 and 36 on the outer bowl 26. The two axes of rotationdelned by the gimbal bearings 3i, 33, and Sil lie as nearly as possiblein a plane with the point of intersection of the axes being as exactlyas possible at the geometrical center of the outer surface of inner bowl21, which is the same point as the center of the inside surface of theouter bowl 2S.

With this arrangement, and khaving a gravity meter in the container 353,it and the spherical bowl 21 will rotate about the gimbal suspensionpoint until the center of gravity is directly beneath. Since thisrotation will not vary in any' distinguishable amount the depth cisubmergence of the bowl 21 in the fluid 2B, as the volumeof the space 2Bremains constant for all position of the inner `bowl 21 relative toouter bowl 2G, it will be seen that the buoyant force of liquid 29 onthe inner bowl 2? will never vary. Consequently, the suspended system(container 3u and bowl 21) is as free to level itself in the liquid as apendulum suspended in air or vacuum. On the other hand, the liquid 29 inthe space 28 exerts a very beneiicial damping action due to itsviscosity, so that the inner bowl 21 is very rapidly brought to restrelative to the outer bowl 26. Further, as a substantial portion, orpreferably all of the support of the inner bowl 21 and gravity meter incontainer 30 can be provided by the buoyancy of fluid 29, gimbalbearings 3l, 33, and 34 can be extremely delicate and sensitive, theirprimary function being thus lto hold the inner bowl centered within theouter. The buoyancy of the ilud 29 in this arrangement has a stillfurther beneficial effect in that if in any way the pivot bearingsbecome damaged so that the pivoting-is displaced to one side or anotherfrom Athe exact center of the spherical bowl surfaces, the torque of thebuoyancy is in the opposite direction Afrom the torque of the suspendedmass about the displaced pivot point. For example, assume that thepivots are completely shifted to the right-hand edge of the inner bowl21. The suspended system .would the surface oi a castdesired and aretypically experience a torque in a countercl'ockwise direction about thenew pivot point. However, the buoyancy in the fluid 29 creates aclockwise opposing torque, which is exactly equal if the suspendedsystem is exactly buoyantly supported. Consequently, leveling errors dueto defective pivoting can be almost or even completely eliminated.

Of interest to this suspension also is the manner of establishingelectrical connections to the delicately suspended gravity meter withinthe container 30 without introducing torques which interfere withleveling of the container and bowl 21. This is accomplished preferablyby bringing the separate electrical leads within the cable I6 out to astationary mounting strip liti, from which each lead is extended by ahair spring M to an insulated connecting point on an extension 42 of theouter gimbal shaft. These hair springs ill are highly resilient and arekept from contacting each other by thin discs of insulation 43. A bundleof insulated leads lifl carries the electrical circuits from the tips ofhair springs #il around the gimbal bearing 3B to the ginibal ring 32,whence the circuits are transferred by a similar set of hair springs 45to the inner gimbal shaft through the gimbal bearing 3l, and thence to aconductor bundle dii mounted on the casing 3S. In this manner electricalconnections are carried past the delicate gimbal bearings withoutintroducing difiiculties due to sliding friction of slip rings and thelike, which could prevent proper leveling of the instrument.

It will be noted that considerable free space is provided around thesupport arms 35 and 36 by making the outer bowl taller than the inner sothat the inner bowl 21 can swing through a considerable angle. Theinstrument mounting is thus adapted to beset upon a marine bottom l2having considerable tilt. In order to prevent splashing or leakage offluid 29 out of the space 28, as well as to prevent swinging of theinner bowl 2l during handling, the rim of inner bowl 21 is provided witha collapsible pneumatic tube 5t inilated or deflated at will by a pump5i driven by a motor 52 remotely controlled through the cable te. Wheniniated, tube 5e both seals against the inner surface of outer bowl 2Gand holds the inner bowl 2 clamped to it. When deiiated, as shown, theinner bowl swings freely.

In order to bring instrument holder 30 and inner bowl 2'? to the desiredposition for leveling the gravity meter in holder 36, a pair of weights55 and 56 movable along screws 51 and 5S iixed to the gimbal-suspendedassembly are provided.

The outer bowl 26 is preferably shock-mounted within the pressure shells2l and 22 by a cushion of sponge rubber Ed at the base of shell 22 and aresilient rubber ring 6i between the shell 2| and the open top of thebowl 255. A highly desirable type of iluid 29 for partially filling thespace 2S between the bowls is one-oi the recently developed siliconeshaving a substantially constant viscosity with varying temperature, aswell as greater specilc gravity than many fluids. However, have foundthat ordinary automotive lubricating oils of such viscosities as SAE-30or 40 are also suitable for this use, although in such event thesuspended system may beonly partially buoyancy-supported. Completesupport of the system by oil is, of course, possible by sufficientlyenlarging the size of the inner and outer spherical bowls.

While I have described my instrument vmounting in connection with amarine .type of gravity meter, it is to be understood that it is .alsouseful in connection `with other .typesofV` instruments .res

quiring very accurate leveling, either on water or land, and it is alsoapparent that modifications and variations may be made of the principleof operation which has been described. The invention, therefore, shouldnot be considered as limited to the exact details of the describedembodiment, but is to be ascertained from the scope of the appendedclaims.

I claim:

l. A self-leveling mounting for a gravity meter comprising an outerspherical bowl having a smooth inner surface, a pendulous innerspherical bowl of smaller diameter than said outer bowl and having asmooth outer surface, a gimbal mounting pivotally connecting said innerbowl concentrically within said outer bowl, the axes of rotation of thegimbal bearings intersecting at a point which is the geometrical centerof the concentric spherical surfaces of said bowls, a body of liquidonly partially lling the space between the bowls and at least partiallybuoyantly supporting the weight of the gimbal-suspended system, and agravity-meter holder xed within said inner spherical bowl.

2. A self-leveling mounting for a gravity meter comprising an outermember having a smooth inside surface of spherical form, a pendulousinner mem-ber having a smooth outside surface of spherical form ofsmaller diameter, a gimbal mounting suspending said inner member withinsaid outer member with said inside and outside surfaces concentric andleaving a space of uniform width between them, a liquid only partiallylling the space between said surfaces and substantially entirelybuoyantly supporting said inner member, and a gravity-meter holder fixedwithin said inner member.

3. A self-leveling mounting for an instrument requiring a plurality ofelectrical leads comprising an outer member having an inside surface ofspherical form, an inner member having an outside surface of sphericalform of smaller diameter than said inside surface, a gimbal ring pivotedto said outer member, said inner member being pivoted to said ring sothat said surfaces are concentric, leaving a space of uniform widthbetween them, a liquid partially iilling said space and at leastpartially buoyantly supporting said inner member, three groups ofinsulated electrical leads fixed respectively to said outer member, tosaid ring, and to said inner member, a highly resilient springconnecting each of said leads on said outer member to a correspondinglead on said ring, a similar spring connecting each of the leads on saidring with a corresponding lead on said inner member, and an instrumentholder xed within said inner member.

4. A self-leveling instrument mounting comprising an outer sphericalbowl, an inner spherical bowl of smaller diameter and substantially lessheight than said outer bowl, a gimbal mounting concentrically suspendingsaid inner bowl within said outer bowl and leaving a space of uniformwidth between them, a body of liquid partially lling said space,clamping means xed on said inner bowl and adapted both to contact saidouter bowl across said space and to conne said liquid within said space,means for actuating said clamping means, and an instrument holder xed tosaid inner bowl.

References Cited in the ille of this patent UNITED STATES PATENTS NumberName Date 2,179,467 Cox Nov. 7, 1939 2,260,396 Otto Oct. 28, 19412,384,739 Hasbrook Sept. 11, 1945 2,500,410 Hewitt Mar. 14., 19502,513,044 Page June 27, 1950 FOREIGN PATENTS Number Country Date 311,426Germany Mar. 21, 1919

